Modelling of aggregation and disaggregation of optical properties and surface temperatures over urban area in infrared domain

This paper presents an aggregation model of optical properties and surface temperatures over urban area in the infrared domain (3-14 mum). The landscape viewed by an airborne or space borne sensor is assimilated as a homogeneous and flat surface, called equivalent surface. The aggregation process aims to define equivalent reflectance, emissivity and surface temperature related to this equivalent surface. These equivalent parameters are determined from radiances measured at-sensor level and depend on several factors (surface geometry, sensor position, etc.). Their spectral and directional behaviours are studied using a Design Of Experiments (DOE) approach. The aggregation model is tested on two cases, a rough and heterogeneous surface type ldquovalleyrdquo and an urban canyon. The results show that the equivalent parameters depend mainly on the surface intrinsic parameters. But, other factors must not be neglected, especially to retrieve the elementary parameters of observed area. It consists to disaggregate the equivalent parameters by inverting the aggregation equations. Such unmixing method is proposed from spectral and directional equivalent optical properties and temperature. For the two processed cases, the results are very satisfactory with an accurate of 0.01 for reflectance and emissivity and an accuracy of 1K on the surface temperature.